Cooper

I guess this has been raised before but couldnt find anything in the search.

I have a 92C4 coupe which seems to have a problem as follows.
If I accelerate hard in say second gear, and move to third and not accelerate as hard, the engine seems to hesitate in its acceleration, it also does it sometimes when I DO want to continue the thrashing (more embarrassing).
It is not really bad, but wonderd if anyone else had encountered it.
It also becomes apparent if I let the revs come down slowly from speed and then try to pick up speed a little.
i have drilled my airbox but apart from that no other mods.
Could an Oxygen sensor cause this, or perhaps a leaky cat??
Has anyone replaced a cat with bypass?

Any help appreciated.

Andy Roe

Cooper,

Have you checked the condition of your Distributer Rotor Arms or the Distribuer belt?

It might be dirty fuel?

Andy

John Boggiano

Is this all the time, Cooper, or just when the weather's really hot.

(Note to those not in the UK - it really has been!)

Cooper

Now you mention it it has just been recently that I have noticed. My caps and arms are new and the belt looks like new according to JZ machtech.

Can anyone reccomend a good additive to clean injectors?
Might be worth a try or else Ill clean my flow meter.
Thanks lads.

springer3

There is a tuning flap in the intake system. It opens at high power settings to improve breathing. It needs to close at low RPM for smooth idle and low end torque. Is it possible the flap is stuck in the high power (open) position? That would cause rough running and poor power at low RPM and low power. I have not experienced this problem, but operation of the tuning flap is one of the first things I would check if I had a problem only at one end of the power range. Good luck, and let us know what you find!

Bob Krantz

Cooper:
Here are some things I have checked/changed/fixed over several episodes of misfiring:

Fuel pump pressure and quantity
Spark plug wires
Caps and rotors
Cylinder head temp sensor
Air flow sensor
All electrical connections (especially ECU main plug)
DME relay
Fuel pump relay
Alternator output
Battery and terminal condition/connections
Oxygen sensor
Bad gas?
Leaking intake manifold boot
Leaking oil filler cap seal (and any other source of vacuum leak)
and more...

I have had 3 major episodes of hesitation over about 5 years; the most severe instances made the car almost stall. The most recent bad behavior went away after I noticed the A/C hose binding on part of the throttle linkage--vacuum control(?). After moving the hose (and resetting the DME) the miss went away. The frequency of similar posts makes me think that a number of subtle problems can cause the same poor running, and that one by itself may not be noticeable. But when 2 or more kick in, the car hesitates. This makes repair challenging, since you may have to track down multiple problems. By the way, each time, the onboard system reported no faults.
Bob K
1989 C4

Cooper

Cheers chaps.
Ill see what happens when I reset the DME this weekend

Rob McConnell

Hi There

I met up with a guy from the Smartgroup board who had the same problem. I did not believe it until i went in his car, you could be running along at 60mph and the car would almost stall and then immediately pick up after a second or so.

This was a very scary experience for me. Put him in touch with my mechanic who tracked it down to the air flow meter i think, took it apart and something was pitted inside it. This was over a year ago so my memory is not so good.

Post a mail on Smartgroups asking for "Attn Jerry in Jersey UK". He could offer the answer.

Regards
Rob 91 964 cab
Jersey UK

Cooper

Thanks, but I think I must have misquoted my problem.
It is no where near as severe as almost stalling, indeed it is just a sort of breathlessness when changing up through the gears.
It is probably not even noticable by a passenger, I'm probably just a bit paranoid, but I'm not alone eh??????